In recent years, standardization of Long Term Evolution (LTE) as a next generation mobile radio communication technique has been proposed in the 3rd Generation Partnership Project. In this proposal, various techniques for improving frequency utilizing efficiency have been discussed.
To improve the frequency utilizing efficiency, a radio base station device is desired to perform controlling (scheduling) for efficiently allocating an uplink radio resource that is to be used in a data communication between a radio base station device and a mobile station, that is, a resource that may be indicated with a frequency and a time to many mobile stations under control of the radio base station device.
As one of the methods, the mobile station reports a resident amount of data stored in a transmission buffer to the radio base station device, and the radio base station device determines an uplink radio resource amount to be allocated to the mobile station according to the data resident amount. According to this method, a Buffer Status Report is used to report the resident amount of the data stored in the transmission buffer of the mobile station.
The following Patent Document and Non-Patent Documents propose mobile radio communication systems that schedule allocation of the uplink radio resource based on a buffer status report signal:    [Patent Document] Japanese Laid-open Patent Publication 2009-49580    [Non-Patent Document 1] 3GPP TS36.211Ver8.9.0:3rd Generation Partnership Project Technical Specification Group Radio Access Network Evolved Universal Terrestrial Radio Access (E-UTRA) Physical Channels and Modulation    [Non-Patent Document 2] 3GPP TS36.212Ver8.8.0:3rd Generation Partnership Project Technical Specification Group Radio Access Network Evolved Universal Terrestrial Radio Access (E-UTRA) Multiplexing and channel coding    [Non-Patent Document 3] 3GPP TS36.213Ver8.8.0:3rd Generation Partnership Project Technical Specification Group Radio Access Network Evolved Universal Terrestrial Radio Access (E-UTRA) Physical layer procedures    [Non-Patent Document 4] 3GPP TS36.321Ver8.8.0:3rd Generation Partnership Project Technical Specification Group Radio Access Network Evolved Universal Terrestrial Radio Access (E-UTRA) Medium Access Control (MAC) protocol specification.